Chapter 88 Diseases of the Penis and Prepuce
Animals with diseases of the penis and prepuce can be presented for a variety of clinical signs. Commonly, discharge or hemorrhage from the prepuce is the presenting complaint. Other clinical problems associated with penis and prepuce disorders are abnormal urination, neoplasia, inability to mate, or persistent penile erection. Urethral diseases are discussed in Chapter 81.
ETIOLOGY
Congenital Disorders of the Penis and Prepuce
Persistent Penile Frenulum
• During the perinatal period, the surface of the glans penis and the preputial mucosa separate. When this separation fails, abnormal connective tissue, most commonly joining the ventral midline of the distal penis and prepuce, persists, resulting in the inability of the penis to extrude fully from the prepuce.
Hypospadia
• Hypospadia results from abnormal closure of the urethral tube during development and can cause one or more abnormal urethral orifices located anywhere along the length of the urethra.
• Most commonly, the abnormal orifice is located along the ventral aspect of the penis and prepuce, but it may extend through the scrotal region to the perineal region. The condition is due to incomplete masculinization during development, and it can be associated with an underdeveloped penis and/or with preputial malformations.
• An androgen receptor defect is responsible for lack of normal penile development under the influence of dihydrotestosterone.
Penile Hypoplasia
• Hypoplasia can occur with failure of masculinization, as seen in androgen receptor defects, and has been observed in both dogs and cats.
• Ambiguous genitalia can be found in XX sex reversal syndromes. Affected dogs can exhibit multiple penile and preputial abnormalities and are sterile.
• Female pseudohermaphroditism, in which the chromosomal sex is XX and ovaries are present, results from the presence of androgens during fetal development. Affected animals can exhibit clitoral enlargement or any degree of penile development, which can mimic penile hypoplasia.
Acquired Penile Disorders
Priapism
• Priapism is defined as persistent, abnormal penile erection and is due to failure of venous outflow of blood from the erect penis.
• The causes are often not well understood. A persistent erection that is associated with hyperactive behavior or sexual arousal is not considered priapism. Also, priapism must be differentiated from other disorders that cause persistent swelling of the penis, such as hematomas that can be observed in association with trauma or coagulopathies.
Trauma
• There are numerous causes of blunt or penetrating trauma that can affect the preputial region and possibly the penis in small animal patients.
• Penile damage may be clearly evident in some animals presented as trauma emergencies. In other animals, trauma to the penis, due to such causes as animal bites, mating mishaps, human malice, or iatrogenic trauma from repeated catheterizations, can present with preputial discharge and swelling, pain, fever, or other signs of inflammation.
Foreign Body
• Foreign bodies can become lodged within the prepuce surrounding the penis and can create significant damage and inflammation.
• Grass awns, mulch, other plant materials, or small particulate materials can lodge with the prepuce, creating significant inflammation and resultant balanoposthitis.
Neoplasia
• Benign and malignant neoplasms involving the prepuce and penis are relatively uncommon in dogs and cats.
Transmissible Venereal Tumor
• This tumor is usually seen in young dogs and presents as a reddened, irregular mass on the mucosa of the penis.
Balanoposthitis
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